Diego Sierra, a 20-year-old Latino male, was shot and killed on March 5, 2025, in Whittier, California. He suffered a gunshot wound to the neck and was pronounced dead at 10:35 p.m. while in an ambulance. The shooting took place on Newlin Avenue between Walnut Street and Mar Vista Street after gunfire erupted from an apartment area along the west sidewalk; Sierra was inside a white Tesla that continued east on Mar Vista Street and then south on Greenleaf Avenue before stopping near a fire station.

Emergency responders sent at least two ambulances to the scene and a third person, possibly a family member, was later transported after a severe anxiety attack. Family members gathered at Walnut Street and Greenleaf Avenue; distress was audible over emergency radio communications. No arrests or suspects have been named in connection with this homicide. Anyone with information about the shooting on Newlin Avenue is asked to come forward.